1. Technical Field of the Invention
The present invention relates to a photoelectric smoke detector utilizing a light emitting element and a light receiving element.
2. Background Arts
Photoelectric smoke detectors used to mainly detect smoke associated with fire occurring in indoor space, but in recent years have come to be also used as one means adapted to quickly detect device abnormalities while being installed in a device, such as a semiconductor producing device, a machine tool, a switchboard, an industrial controller, or the like.
As described above, although installed in different targets, smoke detectors for use in a device also have the same configuration as that of the smoke detectors for use in indoor space, and many of them have been downsized while keeping this configuration.
FIG. 4 show a configuration of a conventional typical photoelectric smoke detector (see Patent Document 1 for example).
The conventional photoelectric smoke detector 1 is, for example, as shown in FIG. 4(A), installed on the ceiling or the like in such a manner that a chamber part 2 having a plurality of inlet and outlet ports circumferentially provided as smoke introduction and extraction ports are oriented downward so that the smoke travel direction can be disregarded. Inside the chamber part 2, as shown in FIG. 4(B), a light emitting element 3 and a light receiving element 4 are arranged so that optical axes intersect with each other at approximately 120 degrees. Smoke enters into a detection area AR located near the intersection between the optical axes, and light emitted from the light emitting element 3 is scattered by the smoke and reaches the light receiving element 4, thereby achieving detection of the presence of smoke. To prevent erroneous detection under an absence of smoke, a plurality of labyrinths 5 are arranged circumferentially so as to eliminate disturbance light, also even when light emitted from the light emitting element 3 is reflected, prevent this light from traveling toward the light receiving element 4, and further avoid preventing the entry of smoke into the detection area. Around the plurality of labyrinths 5, an insect screen 6 is provided for preventing entry of insects from entering into the interior space.
Moreover, there conventionally exists a photoelectric smoke detector, as described in Patent Document 2, which introduces smoke to an optical chamber through only one opening provided at a bottom surface and which detects the presence of smoke through functions of a light emitting element and a light receiving element provided on the left and right side surfaces of the optical chamber.
[Patent Document 1] Japanese Patent Laid-Open No. 1996-166347
[Patent Document 2] Japanese Patent Laid-Open No. 1992-160698